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Biomedical subjects

J Bonnet

Publications and source records attributed to J Bonnet.

At least 73 records · Page 4Linked to original sources
PubMed1996

A water-soluble, stable dipeptide NK1 receptor-selective neurokinin receptor antagonist with potent in vivo pharmacological effects: S18523.

The potassium salt of a chemically stabilized dipeptide, {1-[4-(1 H-tetrazol-5-yl)butyl]indol-3-yl}carbonyl-Hyp-Nal-N(methyl)-Bzl , (Hyp = (R)-4-hydroxy-L-proline; Nal = 3-L-(beta-naphthyl)-alanine), S18523, is described as a new water-soluble, potent and selective NK1 receptor antagonist. The low molecular weight antagonist (M(r) = 736) displays nanomolar potency (pA2 = 9.6) in the rabbit vena cava (NK1) bioassay and nanomolar affinity (pKi = 9.1) on the human NK1 receptor expressed by lymphoblastoma cells. It is devoid of mu-opiate affinity (Ki > 10(-4) M with respect to tritiated Tyr-DAla-Gly-MePhe-Gly-ol), has negligible calcium-channel affinity (estimated Ki = 2.6 x 10(-5) M, with respect to isradipine) and does not cause peritoneal mast-cell degranulation. S18523 has strong antinociceptive effects in three classical pain tests in vivo both by i.v. and p.o. routes. The dipeptide potently antagonizes bronchoconstriction provoked by exogenous substance P in the guinea-pig and acts longer than the non-peptide antagonist CP99994, when administered as aerosol. Finally, S18523 displays antiinflammatory properties, since it dose-dependently inhibits substance P-induced plasma extravasation both in the bladder (ID50 = 0.18 mg/kg i.v.) and bronchi (ID50 = 0.14 mg/kg i.v.) of the guinea-pig.

Animals↗
PubMed1996

Monocyte/macrophage recruitment and expression of endothelial adhesion proteins in human atherosclerotic lesions.

Since mononuclear cells are recruited in atherosclerotic lesions, the expression of adhesion proteins by the arterial endothelium may play a major role in atherogenesis. The relationships between ICAM-1, E-selectin, and VCAM-1 expression on the arterial endothelium and the presence and degree of maturation of intimal macrophages in human atherosclerotic lesions was investigated. By quantitative double immunostaining with a pan-macrophage-specific monoclonal antibody, HAM-56, and a recently developed monoclonal antibody that is specific for mature macrophages, 3MA-B38, arterial sections were classified as (I) normal, (II) thickened without macrophage infiltration, (III) atherosclerotic with recent macrophage infiltration or (IV) atherosclerotic with infiltration of mature differentiated macrophages. A marked increase in the expression of ICAM-1, E-selectin, and VCAM-1 was observed on endothelial cells adjacent to recently recruited macrophages. Endothelial cells overlying differentiated macrophages exhibited a lower but significant increase in VCAM-1 expression, with no difference in ICAM-1 and E-selectin expression with respect to that observed in endothelium of normal arteries. These findings indicate that the endothelium covering the human arterial wall exhibits different states of activation as reflected by the expression of adhesion proteins, and that intimal monocyte/macrophage recruitment appears to depend on the level of expression of adhesion proteins.

Adult↗
PubMed1996

Effect of chromatic errors in microscopy on the visualization of multi-color fluorescence in situ hybridization.

The relevant microscopical conditions for the optimal visualization of ratio-color FISH stained cells were investigated. Special attention was given to the influence of the type of illumination, (semi)-critical vs. Köhler type illumination, in combination with the use of multi-band excitation and emission filters, on the registration of the colors of ratio labelled probes. Due to chromatic errors, many collecting lenses were found to cause a wavelength dependent excitation pattern with critical illumination. This resulted in a change of the observed color of microscopic objects when stained with a mixture of two dyes and excited with a dual band pass filter. A quantitative study of this effect for semi-critical illumination of FISH ratio-labelled chromosomes revealed a difference of 20% between highest and lowest ratio values depending on the position of the object in the microscopic field vs. only 2.5% for Köhler type of illumination. The impact of these errors on the identification of ratio-labelled probes and on the sensitivity of comparative genomic hybridization (CGH) to detect gene amplifications or losses is discussed. Standard preparations consisting of solutions of defined mixtures of fluorescent dyes or objects stained with defined ratios of fluorophores, are proposed to correct for the errors observed.

Artifacts↗
PubMed1996

Effects of parathyroid hormone and agonists of the adenylyl cyclase and protein kinase C pathways on bone cell proliferation.

The anabolic effect of parathyroid hormone (PTH) on bone is partly due to a stimulation of osteoblast proliferation. The PTH signal is transduced by the pathways of adenylyl cyclase (AC)/protein kinase (PK) A and phospholipase C/PKC/Ca++. There is still uncertainty about the relative contribution of the two pathways to the proliferative effects of the hormone. In our study, PTH(1-34), AC/PKA agonists, and phorbol 12-myristate-13-acetate (PMA, a PKC activator) stimulated cell proliferation in cultured mouse calvariae. In isolated osteoblasts, only PMA stimulated proliferation, whereas AC/PKA agonists and PTH(1-34) inhibited it. As already known, PTH in the presence of supramaximal concentrations of transforming growth factor-beta (TGF-beta) stimulated osteoblast growth; under these same conditions, AC/PKA agonists reproduced the stimulatory effect of PTH(1-34), whereas PMA became inhibitory. PTH(1-31), which stimulates AC without affecting PKC, acted similarly to the fully active PTH(1-34) in both calvaria and isolated osteoblasts. On the contrary, midregion fragments that activate only PKC stimulated calvaria cell proliferation faintly in comparison with PTH(1-34); no effect was seen in osteoblasts, either with or without TGF-beta. Our study shows that the effects of PTH on proliferation can be mimicked by agonists of the AC/cAMP pathway. Although PMA is indeed able to stimulate cell growth in tissue explants, its effects on isolated osteoblasts markedly diverge from those of PTH. We conclude that activation of the AC/PKA pathway is the main component of the proliferative effects of PTH.

1-Methyl-3-isobutylxanthine↗
PubMed1996

[Systemic embolism and thrombosis of the left atrium in a patient in sinus rhythm with cardiac amyloidosis].

The authors report the case of a female patient admitted for complete heart failure with a diagnosis of type AL amyloidosis associated with dysglobulinaemia. While in hospital, she developed femoral embolism found to be secondary to atrial thrombosis in the absence of any supraventricular arrhythmia. The frequency and mechanism of intracardiac thrombosis and embolic accidents in cardiac amyloidosis are discussed in the light of this case.

Aged↗
PubMed1996

[Value of echocardiography-dobutamine in the study of reserve myocardial contractility in aortic stenosis with alteration of left ventricular function. Apropos of a case].

The authors report a case of tight aortic stenosis, without coronary artery disease, presenting with heart failure, alteration of global left ventricular contractility and a low gradient. Increasing-dose dobutamine echocardiography demonstrated an improvement of myocardial contractility and an accentuation of the transvalvular gradient. The place of this examination in the therapeutic strategy and follow-up of the disease is discussed in the light of the current data of the literature.

Aged↗
PubMed1995

Improved leishmanicidal effect of phosphorotioate antisense oligonucleotides by LDL-mediated delivery.

We have designed antisense oligonucleotides that can interact with lipoproteins in order to use them as vectors to facilitate the uptake by those cells expressing the corresponding receptor. Phosphorothioate (PS) oligonucleotides were linked at the 5' end to a palmityl group giving rise to PSPal conjugates. Such a modification enables the oligonucleotide to form a stable non-covalent complex with low density lipoproteins (LDL) through hydrophobic interactions. The antisense effect of LDL-oligonucleotide complexes was assayed by targeting the mini-exon sequence of Leishmania amazonensis in infected mouse peritoneal macrophages. A 16-mer antisense PSPal oligonucleotide/LDL complex exerted a more pronounced sequence-specific effect than the free oligomer: about 25% and 10% of infected macrophages were cured by a 48 h incubation in the presence of 2.5 microM of the complexed and the free oligomer, respectively. When oxidized LDL was used instead of the native one for complexation, a further 2-fold increase in the antisense effect was observed suggesting that alternative (unregulated) scavenger receptor can be used for more efficient delivery of antisense oligonucleotides into macrophages. In addition, a significant reduction of the parasitic load was observed in those cells that were not fully cured.

Animals↗
PubMed1995

Predictive value of hemostatic factors for sudden death in patients with stable angina pectoris.

To assess hemostatic risk factors for sudden death in patients with stable angina, 323 consecutive patients were recruited prospectively. Patients with clinical heart failure or recent myocardial infarction were excluded. The following clinical variables were recorded: age, gender, smoking habits, hypertension, previous myocardial infarction, left ventricular hypertrophy, and severe ventricular arrhythmia. Angiographic variables included coronary extent, assessed from Jenkins' and mean atherosclerotic scores, and left ventricular ejection fraction. Lipid variables included total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and apolipoproteins A-I and B. Hemostatic factors included fibrinogen, fibrinopeptide A, antithrombin III, factor VIII antigen, factor VIII coagulant, protein C, plasminogen, alpha 2 antiplasmin, euglobulin clot lysis time, tissue plasminogen activator before and after venous occlusion, and plasminogen activator inhibitor. There were 34 deaths, 19 of which were sudden during the follow-up period (60 +/- 17 months). The association between each variable and the risk of sudden death was assessed by calculating the relative risk with the Cox univariate model. All significant predictors from the univariate analysis were then incorporated in a Cox multivariate model to select the independent predictors of sudden death. The independent predictors of sudden death were left ventricular hypertrophy (p < 0.04), lower left ventricular ejection fraction (p < 0.04), and shorter euglobulin clot lysis time after venous occlusion (p < 0.02), whereas fibrinogen (p < 0.07) and Jenkins' score (p < 0.08) were borderline. Determination of hemostatic variables, especially those pertaining to dynamic fibrinolysis, may thus be of value in assessing risk of sudden death.

Analysis of Variance↗
PubMed1995

Characterisation of cyclooxygenase 1 and 2 expression in mouse resident peritoneal macrophages in vitro; interactions of non steroidal anti-inflammatory drugs with COX2.

Resident peritoneal macrophages exposed to inflammatory stimuli (zymosan, lipopolysaccharide (LPS)) represent a widely used model for studying arachidonic acid metabolism and for screening of prostaglandin (PG) synthesis inhibitors. In the present study, cyclooxygenase 1 (COX1) was shown constitutively expressed in mouse adherent and non-adherent macrophages whereas expression of COX2 was observed only in adherent cells, even when cultured in minimal conditions (Ca-, Mg- and serum-free medium). The COX2 expression was amplified by arachidonic acid cascade stimulating agents (Ca, Mg, zymosan) and by LPS in a time-dependant manner; PGE2 by itself amplified LPS-induced COX2 expression. In well-defined experimental conditions of COX2 expression (LPS-stimulated adherent macrophages), we studied specific interactions of some representative anti-inflammatory drugs with COX2 enzymatic activity and expression. By contrast with dexamethasone, which reduced PGE2 release together with a strong reduction of COX2 expression (protein and mRNA), non steroidal anti-inflammatory drugs (NSAIDs) reduced PGE2 synthesis without any effect at the COX2 mRNA level. This reduction of PGE2 production by NSAIDs resulted from either an exclusive enzymatic inhibition (aspirin, NS398, 6-Methoxy naphtyl acetic acid) or an enzymatic inhibition associated with a slight decrease of COX2 protein level (indomethacin). For paracetamol and salicylic acid, two weak inhibitors of COX enzymatic activity, reduction of PGE2 synthesis appeared to be related to reduced level of COX2. These findings show that the macrophage can be used as a cellular model to study specifically COX1 and COX2. In this cell type, COX2 expression is dependent on adhesion, enhanced by stimulation of arachidonic acid metabolism, and auto amplified by PGE2. Furthermore, the results indicate that known NSAIDs differ in their interaction with cyclooxygenase, being able to inhibit either COX2 enzymatic activity, and/or COX2 expression. However, further studies are required to determine the mechanism and the role of COX2 expression during inflammation in vivo, and to define more precisely the best target for new potent and safe NSAIDs.

Animals↗
PubMed1995

Induction of intercellular adhesion molecule-1 by monocyte adhesion to endothelial cells in human culture system.

Increased monocyte adhesion to the endothelial lining of blood vessels by cytokine-inducible adhesion proteins is a crucial event in inflammatory processes. Moreover, adherence is known to induce cytokine gene expression, suggesting a possible positive feedback mechanism. Therefore, we determined whether monocyte adhesion to endothelial cells (ECs) amplifies their adhesion by inducing intercellular adhesion molecule 1 (ICAM-1), and whether such positive feedback mechanism could be mediated by secretion of interleukin-1 (IL-1). Using monocyte-EC couples obtained after monocyte adhesion to ECs, and methods of quantitative polymerase chain reaction and immunofluorescence flow cytometry, we showed a biphasic increase of ICAM-1 mRNA content (2 and 16 hours) and a time-dependent increase of cell surface expression of ICAM-1, mainly on ECs, and couple adhesiveness, after monocyte adhesion to ECs. Anti-ICAM-1 monoclonal antibody inhibited 63% of the enhancement of adhesiveness induced on monocyte-EC couples by previous monocyte adhesion, suggesting that monocyte adhesion to ECs induces an increase of couple adhesiveness which is partially dependent on the ICAM-1 pathway. The early ICAM-1 mRNA induction was associated with a fast induction of IL-1 beta mRNA and a 7.7-fold increase in IL-1 beta protein in supernatant. However, 30% of this 2-hour ICAM-1 mRNA peak was abolished by recombinant soluble human IL-1 receptor, suggesting that the early ICAM-1 over-expression was partially mediated by IL-1 beta, and could be induced directly by adherence. The second ICAM-1 mRNA peak was accompanied by a marked increase in IL-1 beta mRNA and protein secretion (2.6 ng/ml). The binding to ICAM-1 did not appear to directly stimulate IL-1 beta synthesis. These results indicate that monocyte adhesion to endothelial cells appears to stimulate their own recruitment via induction of ICAM-1 thereby constituting a self-perpetuating positive feedback system.

Base Sequence↗
PubMed1995

Specific evaluation of localized bone mass and bone loss in the rat using dual-energy X-ray absorptiometry subregional analysis.

Dual-energy X-ray absorptiometry (DXA), together with the use of ultra-high resolution software, recently appeared as an accurate method for determining bone mineral density (BMD) in the rat. In order to assess the ability of this technique to detect changes in bone mass in the rat rapidly and precisely, we measured BMD at various sites of the femur using DXA subregional analysis. In particular, we studied the BMD of the metaphyseal part of the femur (M-BMD) rich in trabecular bone, and compared the values obtained with the cancellous bone volume measured by histomorphometry. In short-term ovariectomized animals (experiment 1), M-BMD was the only parameter to differentiate statistically between 10 ovariectomized (OVX) and 10 SHAM-operated (SHAM) rats (-11.2%, p < 0.01) 9 days after surgery. M-BMD still expressed the greatest variation between OVX and SHAM rats 42 days following ovariectomy (experiment 2) (-16.1%, p < 0.001 v -6.2%, p < 0.01 for the total femur BMD) and confirmed previous data demonstrating a greater loss of cancellous than cortical bone after cessation of ovarian activity. M-BMD was highly correlated with cancellous bone volume (BV) in normal (r = 0.82, p < 0.001, n = 30), OVX (r = 0.77, p < 0.001, n = 22) and SHAM (r = 0.88, p < 0.001, n = 21) rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1995

Improved microplate immunoenzymatic assay of PCR products for rapid detection of Mycoplasma pneumoniae.

We developed a microtitre hybridization assay for the detection of polymerase chain reaction (PCR) amplified sequences. For this, cloned Mycoplasma pneumoniae DNA containing a sequence complementary to the PCR products is first covalently bound to microtitre wells. These coated microplates can be stored for several months. Then, an aliquot of the PCR product, labelled with digoxigenin-dUTP during its synthesis is hybridized to the immobilized DNA. The use of a rapid hybridization buffer makes this step very short (5 min). Finally, the hybridization signal is detected by an anti-digoxigenin antibody conjugated with alkaline phosphatase. Compared to Southern or other microplate hybridization techniques, this method is cheaper, involved fewer steps and allows easy handling of a large number of samples. This method was used for detection of M. pneumoniae in a series of clinical specimens.

Base Sequence↗
PubMed1995

Myelin P0 glycoprotein: identification of the site phosphorylated in vitro and in vivo by endogenous protein kinases.

Myelin membrane prepared from mouse sciatic nerve possesses both kinase and substrates to incorporate [32P]PO4(3-) from [gamma-32P]ATP into protein constituents. Among these, P0 glycoprotein is the major phosphorylated species. To identify the phosphorylated sites, P0 protein was in vitro phosphorylated, purified, and cleaved by CNBr. Two 32P-phosphopeptides were isolated by HPLC. The exact localization of the sequences around the phosphorylated sites was determined. The comparison with rat P0 sequence revealed, besides a Lys172 to Arg substitution, that in the first peptide, two serine residues (Ser176 and Ser181) were phosphorylated, Ser176 appearing to be modified subsequently to Ser181. In the second peptide, Ser197, Ser199, and Ser204 were phosphorylated. All these serines are clustered in the C-terminal region of P0 protein. This in vitro study served as the basis for the identification of the in vivo phosphorylation sites of the C terminal region of P0. We found that, in vivo, Ser181 and Ser176 are not phosphorylated, whereas Ser197, Ser199, Ser204, Ser208, and Ser214 are modified to various extents. Our results strongly suggest that the phosphorylation of these serine residues alters the secondary structure of this domain. Such a structural perturbation could play an important role in myelin compaction at the dense line level.

Adenosine Triphosphate↗
PubMed1995

Assessment of non-invasive new imaging techniques in the diagnosis of heart liposarcoma.

Two patients, with recurrent acute pericarditis as the first presentation of liposarcoma, were admitted to our department between August and December 1992. The pericarditis was pericardial in one case and retroperitoneal with pericardial inflammation in the other. In contrast to most reported cases, where diagnosis was made post-mortem, diagnosis and surgical decision were based on non-invasive imaging techniques, without cardiac angiography. In cases of recurrent acute pericarditis resistant to usual drugs, new imaging techniques, such as computed tomodensitometry and magnetic resonance imaging, can detect rare causes such as liposarcomas in which prognosis is critically dependent on early diagnosis.

Acute Disease↗
PubMed1995

Progression of coronary artery disease in non-dilated sites in the months following balloon angioplasty: time-dependent relation with restenosis.

There is scant information on the progression of coronary artery disease in non-dilated sites in the months following percutaneous transluminal coronary angioplasty (PTCA) or on its relationship with restenosis. To assess the incidence of this progression and its relationship with restenosis at various times after PTCA, the authors selected 371 consecutive patients who had undergone a first successful PTCA for angina on native coronaries followed by a repeat angiographic study. The angiograms were analysed by a computer-assisted method; progression was defined as a 20% decrease in diameter and restenosis as a 30% decrease in diameter or a return to > 50% stenosis. The relationship between progression and restenosis was analysed in the whole population and then, using the Mantel-Haenszel chi-square test, in two subgroups: patients with a stable clinical state, who were restudied routinely and those whose worsened state had prompted repeat angiography. The relationship was assessed at different times between angioplasty and the repeat angiography. Progression was observed in 80 patients (22%) and restenosis in 155 patients (42%). There was a highly significant relationship between progression and restenosis in the total population (chi 2 = 26.4, odds ratio = 3.9 and P < 0.0003) and in the group of patients that were routinely restudied (chi 2 = 31.6, odds ratio = 5.3 and P < 0.0001), but not in the group of patients in whom restudy was performed because of clinical worsening (chi 2 = 0.13, odds ratio = 1.5 and P = NS). With respect to the length of follow-up, in the total population the relationship was significant only at 6 and 7 months (P < 0.0001), and in the group receiving a routine restudy only at 4-5 and 6-7 months (P < 0.001). Progression in non-dilated sites appeared to be strongly and transiently linked with restenosis, suggesting that PTCA may enhance both restenosis and progression over a short period.

Aged↗
PubMed1995

Reconstruction of 12 MV bremsstrahlung spectra from measured transmission data by direct resolution of the numeric system AF = T.

An investigation of x-ray spectral reconstruction from transmission data by direct resolution of the matrix system A*F = T (using spectral algebra formalism) has been previously presented. The resolution has been done with simulated spectrum. In this paper, the method on a real case of a 12 MV photon beam was tested. A special study of the setup has been made to estimate and reduce the experimental errors that could alter the results. In order to convert F(E) (a fraction of the signal due to a photon of energy E) into photon fluence phi (E), the chamber energy response R(E) has been studied and an approximated analytical function for its representation was proposed. Spectra reconstructed from different transmission data using different attenuators, buildup caps, and ionization chambers have been compared to verify the uniqueness of the reconstructed spectra. To test the validity of the results, dosimetric values, such as Depth Dose Data have been calculated, from our spectrum, using a specific code developed by Kosunen et al. The results show a good agreement between the measured and calculated data.

Models, Structural↗